A mystery religion is any religion with an arcanum, or secret wisdom. In a mystery religion, an inner core of beliefs, practices, and the religion's true nature, are revealed only to those who have been initiated into its secrets. (The ancient Greek term μυστήρια (mysteria) means "initiation", notably in the context of the Eleusinian Mysteries.) Ancient mystery religions of the eastern Mediterranean area generally focused on mythic figures who had descended into Hades and returned or who otherwise exemplified death and rebirth, such as Bacchus, Orpheus, Osiris, and Tammuz.